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Cheap SMD LCR Fixture, the Good, Bad and Ugly
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mawyatt:
That look good, just make sure the cover makes good contact with the main case. Also make sure the main case is making good contact with the copper surfaces.

Actually you don't need to go to this extreme, just making sure everything has a good electrical ground connection is sufficient, this effectively creates a somewhat like Faraday Shield around everything inside the case. You want all the parasitic capacitances to remain fixed, and a good mechanical structure keeps things from moving around.

You folks with these SMD fixtures should consider the DC Bias Adapter, kinda interesting to "see" how the DC Bias capacitance changes with ceramic caps, diodes and such!!

Good work and keep us up to date on your progress :-+

Best,
mawyatt:

--- Quote from: Kean on December 21, 2023, 05:05:51 pm ---
--- Quote from: mawyatt on December 21, 2023, 04:42:38 pm ---Also should mention, when doing the "Open Cal", use something to space the fixture plungers the same distant apart as they will experience when engaged with the DUT. We just use something that keeps the Lever Arm at the proper spacing, a pencil works!!

--- End quote ---

I was just about to write this myself.  But a pencil???  :-//

--- End quote ---

Yeah, works well. It just sits behind the Lever arm between the arm and the low side brass plated (silver) plunger housing. Anything will work as a spacer, since it's not electrically involved.

Best,
Kean:

--- Quote from: mawyatt on December 22, 2023, 01:21:13 am ---Yeah, works well. It just sits behind the Lever arm between the arm and the low side brass plated (silver) plunger housing. Anything will work as a spacer, since it's not electrically involved.

--- End quote ---

OK, I was imagining the graphite being placed between the contacts...  :o
I don't know if your original description made it clear otherwise.

On the topic of your DC bias adapter, I've got some of your PCBs on the bench (5pcs added onto a JLC order) but I've not yet reviewed the BOM or ordered the parts to make one up.
mawyatt:

--- Quote from: Kean on December 22, 2023, 02:05:24 pm ---
--- Quote from: mawyatt on December 22, 2023, 01:21:13 am ---Yeah, works well. It just sits behind the Lever arm between the arm and the low side brass plated (silver) plunger housing. Anything will work as a spacer, since it's not electrically involved.

--- End quote ---

OK, I was imagining the graphite being placed between the contacts...  :o
I don't know if your original description made it clear otherwise.

On the topic of your DC bias adapter, I've got some of your PCBs on the bench (5pcs added onto a JLC order) but I've not yet reviewed the BOM or ordered the parts to make one up.

--- End quote ---

The DC Bias PCBs were designed to fit inside this type 65x110x50 enclosure (sawed in half). Use the latest files for the PCB, they have the BNC terminals correctly spaced and added the fast charge capability (and a few other minor changes) mentioned earlier. We haven't used the latest PCB yet, waiting on a PCB order to piggyback on, which should be soon!!

Anyway, hopefully this DC Bias Adapter works as well for you as it has for us!!

Best,

https://www.aliexpress.us/item/3256801465819165.html?spm=a2g0o.order_list.order_list_main.638.27e31802vJOM1n&gatewayAdapt=glo2usa4itemAdapt

hpw:

--- Quote from: mawyatt on December 22, 2023, 01:17:31 am ---Good work and keep us up to date on your progress :-+

--- End quote ---

So on second tweak as  |O while the connections wires are too thick, also shows the common 2mm diameter connection connector as one was loosely too. :palm:

Finally, last picture, RG178 inner silver wire as more flexible and in addition with torx screws for better alignment. Enlarged also inner holes to 4mm diameter as better to adjust.

May at last, shorten or use different connection cables  :phew:

BTW: The Hantek uses for cap measurements only 2 wires and each time switched on, the open calibration is a requirement.

Hp

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